Process and device for coking of fuels



Aug. 15, 1961 R. K. MEWES ETAL PROCESS AND DEVICE FOR COKING OF FUELS 2Sheets-Sheet 1 Filed Jan. 50. 1957 Aug. 15, 1961 R. K. MEWES ET AL2,996,437

PROCESS AND DEVICE FOR COKING 0F FUELS Filed Jan. 30. 1957 2Sheets-Sheet 2 United States Patent O 2,996,437 PROCESS AND DEVICE FORCOKING OF FUELS Rudolf K. Mewes and Max H. Goebel, Bochum, Germany,assignors to Dr. C. Otto & Comp. G.m.b.H., Bochum, Germany Filed Jan.30,1957, Ser. No. 637,233 2 Claims. (Cl. 202-19) Natural fuels, moreparticularly coal and lignite, are not suited for many purposes withoutfurther preparations, since upon heating they give 01f volatilecomponents in considerable amounts and the fuels break down prematurely,in other words, they do not have sufli'cient stability. Considerablegroups of coals, particularly of small grain size, when heated in closedchambers with exclusion of air, are liable to shrink and form solid cokeafter having given oif their volatile components; the coke consistsmainly of carbon and exhibits considerable stability when burned.

There is a demand to convert fuels, which do not possess the inherentcapability of sintering, into briquettes which are of such stabilityduring binning.

One means to process non-sintering fuels to make coke therefrom consistsof adding binders thereto and shaping them into briquettes which arethen subjected to coking.

The present invention relates to a coking process for such briquetteswhich are made, as a rule, from non-sintering fuels with the addition ofbinders. Coking takes place in a shaft furnace, either continuously orsemi-continuously.

By semi-continuous operation we understand an operation in which feedingof the fuel briquettes is not done continuously, but at short intervalsof about A of an hour to 1 hour, and the briquettes are removed from thefurnace at the same rate.

One of the main difficulties in such a coking process in whichbriquettes are made by addition of binders to the fuel, consists in thatthe binder softens during the gradual heating of the briquettes whichcauses the latter to stick together in the furnace. This can then leadto a cluster formation of the briquettes in the coked goods or in anycase to the formation of pieces which do not have the desired size forlater use, for instance in a boiler for heating purposes or in ametallurgical furnace.

Many attempts have been made to avoid this conglomeration of briquettes.For instance, it has been tried to prevent sintering together of thepieces by controlling the rate of heating. With direct heating of afurnace, use was made of heating units having a width not much largerthan that of the elliptic or cubic briquettes to be formed. However,none of the attempts hitherto made led to any commercial success.

It is the object of this present invention to solve this problem bydevising a process and a furnace for carrying out the same in thefollowing manner:

The heating of the fuel briquettes for the purpose of coking is carriedout in a shaft furnace by means of rinsing gases, i.e. hot gasescarrying off vaporizable constituents of the fuel, which are at leastpartly carried in a current parallel to the goods. More particularly,gas of such high temperature is made to impinge onto the surface of thepile which fills the shaft of the furnace, with such high temperatureand in such an amount that hardening of the briquettes occurs to anextent that a resistant carbonized skin is formed on the surface of thebriquettes. In order to secure such hardening in the binders containedon the surface or, as the case may be, hard- Pzftented Aug. 15, 1961enable components in the fuel itself, the temperature impinging upon thesurface of the pile of fuel should at least be 1,000 C. and should carrya heat load of at least 150,000 kilogram-calories per hour and persquare meter.

Such a load of heat is unusual and has not been used in any of the knowncoking procedures. It should be noted that the hourly heat transfer fiomcoke oven wall to charged coal in cokery furnaces made of ceramicmaterial lies at 4,000 to 8,000 kcaL/h/squ. m. In iron retorts this heataddition has been increased to 10,000- 15,000 kcal.; in processes beingbased on rinsing gases alone the heat load used at the conventional gasvelocities did not exceed 50,000, to 80,000 kcal./h./squ. m. In theprocess according to the present invention vthe heat load may beincreased to 4000,000 kcal./h./squ. m.

Due to the fact that the surfaces of the briquettes are hardened byinstantaneous heating and are converted to coke, to a large extent, theyare very resistant during the further travel through the furnace to thejarring which takes place during the sliding down of the fuel. At thesame time the surface layers have become porous and permit the passageof such gases which are set free during the heat penetration to theinterior of the briquettes. Therefore, the briquettes will no longersinter together. They will also approximately retain the shape in whichthey have been fed into the furnace, except for a certain shrinkagedepending on the kind of fuel and binder.

In order to make sure that there will be a suflicient amount of heat forrapid heating of the surfaces of the briquettes, particularly insemi-continuous operation, when the cold fuel briquettes are fed to theshaft furnace, it is possible to arrange in the furnace directly belowthe feed-in inlet for the fuel, one or several vertical rightangledtriangular inserts which must be capable to store heat to such an extentthat they will be at all times maintained at temperatures between 900 C.and 1,300 0., in spite of the continual or intermittent cooling by thefuel. Such an insert can be so designed that below the same piles offuel descending laterally therefrom will be formed. One or severalburners for rinsing gas open into the space above the surface of thepile. The gases introduced through the burners do not only impinge onthe surfaces below the insert, but heat also the vertical right-angledtriangular insert itself with the recently charged fuel descending alongthe upper faces of the insert in a thin layer.

Even if no such vertical right-angled triangular inserts are provided,gas burners should be arranged from which gas impinges immediately uponthe surface of the pile. Inlet openings for the fuel may be on oppositesides of the shaft, while one or several burners for the rinsing gas maybe arranged centrally in the shaft. The inlet openings for the fuel maybe arranged in more than two rows and between each of them burners forthe rinsing gas may be arranged. The rinsing gases may be flue gas, towhich steam or return gas has been added; in addition to combustiblegases, a certain amount of oxygen, for instance air, may be admittedthrough the burners in order to obtain as intense a heating action aspossible, provided that the oxygen addition does not lead to any markedcombustion of the surface layers of the briquettes.

The invention will now be more fullydescribed with reference to theaccompanying drawings, in which several embodiments of the furnace havebeen illustrated by way of exemplification and not of limitation; itshould be understood that many changes in the details can be madewithout departing from the spirit of the invention.

In the drawings:

FIG. 1 is a longitudinal section through a furance according to theinvention with built-in recuperators and a diagrammatic showing of thegas circulation;

FIG; 2 is a transverse section through two furnace shafts arranged inseries;

FIG. 3 is a longitudinal section through a difierent embodimentof afurnace shaft, the bottom part being broken away; and

FIG. 4 isyet another embodiment in similar showing.

Referring now to FIGS. 1 and 2, a furnace shaft is designated by 10; itis of substantially square cross-section and is bounded by a recuperator11 on two sides. At the top of the shaftan inlet opening 12 is provided,and 13 designates a vertical right-angled triangular heat-storage bodyextending from one wall of the shaft to the opposite wall. Burners 14serve for admission and generation of rinsing gas; they are arranged inwalls 18 of thefurnace. In the central portion of the shaft, dischargeopenings 15 are provided for the escaping gas. A chamber 16 topped byvertical right-angled triangular slats 31 serves for admission ofcooling gas. At the bottom an opening 17 is provided for the dischargeof the final product, coke.

The storage body 13 is in the shape of an overhead structure withlateral ledges 20 below which the descending fuel accumulates and formsa space 21 into which the burners 14 are opening. The storage body ismaintained at a temperature of, for instance, 1300 C. The fuel slidingalong the top of the storage body in a moderately high layer, issubjected to high heating accompanied by a marginal coking of the piecesof fuel. The rinsing gas passes from the space 21 down through the'fueland serves for providing an additional amount of heat thereto, so thatcoking proceeds into the interior of the briquettes. During thisprocedure, the gases cool down to for instance 900 C. and are withdrawnthrough openings 15 into the outer chamber 22 of the recuperator; fromthere they escape through pipes 23 arranged at the top and pass into ascrubber 25 provided with a sprinkling device 24. A suction pump 26serves for maintaining a vacuum within the shaft and urges cooled gaspartly through pipeline 27 into the chimney (not shown), partly via line28 into space 16. Valves 29 and 30' are arranged for controlling theamount of the returned gas. Gas ascending from space 16 through thevertical right-angled triangular slats 31 is heated while passingthrough the descending fuel, simultaneously cooling the latter, andlikewise arrives at the discharge openings 15. Through the recuperator,a mixture of rinsing gas and cooling gas is 'thereforepassing upward.The recuperator is equipped with heating tubes 32 which are partly fedwith heating gas, for instance generator gas, partly with air. Bothgases arrive by means of pipelines 33 at the burners 14 where they aremixed.

In FIG. 3 another embodiment of the device according to the'invention isshown in its upper part, thelower part being broken away. The shaft isagain designated by 10, the ,recuperators by 11, the feeding opening 12admits fuel to the shaft over the vertical right-angled triangularinsert body 13. The main diiference between this arrangement and the oneshown in FIGS. 1 and 2 consists in the provision of additional burners38 above the surface of the pile of fuel 39. Pipelines 40 and 41 leadfrom collecting chambers 42 for the heated rinsing gas to burners 14below the storage body 13, and to burners 38. In this arrangement thefuel is therefore heated at once at 39, when it enters through feedopenings 12, and again later when .it arrives at the surface 21 belowstorage body 13. The heat acting on the fuel is therefore intense.

In the embodiment shown in FIG. 4, the shaft is again designated by 10,the recupenator by 11. The main difference between this embodiment andthe others discussed above, consists in the absence of a storage body13. There are two feed openings 43 for the fuel which are arrangedlaterally in the shaft, the burners 44 are again centrally arranged. Inthis way it is accomplished that a large surface of the descending fuelis exposed to the action of the burners.

The invention will now be described in more detail by the followingexample. However, it should be understood that this is given by way ofillustration and not of limitation, and that many changes in details canbe made without departing from the spirit of the invention.

Example The briquettes to be employed are made from coke fines oranthracite with a binder. The binder consists of coke tar pitch andconstitutes 10 to 15 percent of the total. Bitumen can be used insteadof the pitch. An other addition to the briquette is 10 to 20 percentcoking coal. The briquettes are manufactured on a rolling press or anyother suitable press in a known manner and are given the customaryshapes, e.g., egg, nut, cube, oblong or the often-used pillow shape,which latter form is preferred. The weight of the individual briquettelies between 50 g. and 3 kg. and depends upon the size of the blastfurnace or similar appliance in which the coke produced is to be used.

The briquettes are charged into the furnace through opening 12 and areheated by means of the burners installed in the upper part of thefurnace shaft. The temperature is advanced to approximately 600 C.within 20 to 25 minutes. During this time, a carbonized skin forms onthe surface of the briquette which is of suflicient strength to preventbreaking or pulverization of the briquette when new briquettes areadded.

During heating of the briquettes, the rinsing gases cool down toapproximately 800-900" C. They move downward together with thebriquettes and are drawn oif through the outlets 15. Depending upon thesize of the briquettes, a time of 4 to 12 hours is required for thetravel of the briquettes from the charger to the height of the outlets15. During that time, after-cooking occurs.

The rinsing gases are conducted to the heat exchangers 22 by way of theoutlets 15 where they are cooled, and

1 subsequently are purified in the scrubber 25. Pump 26 generates thevacuum necessary for removal of the rinsing gases. Part of the cooledand purified gases is conducted into the lower part of the shaft furnacethrough line 28. It rises counter-currently to the downward movingbriquettes, cools these to approximately 200 C. and is drawn off throughthe openings 15 together with the hot rinsing gases which come from theupper part of the furnace.

The cooled briquettes are removed at point 17 by means of a rollerconveyor or other known means.

A suitable material .having high heat storage capacity, for use in theinsert 13, consists of high-density fire clay which has aheatconductivity of a: 1.53 kcal./m./ C./h. (kilogram calories per meter,degree centigrade and hour) and which has a porosity of approximately 20percent.

What we claim is: I

1. A process for coking briquettes made of solid fuel in a shaftfurnace, which comprises feeding solid briquetted fuel in intervals of15 to 60 minutes from the top 'into said shaft so as to form a pile witha sliding upper surface in said shaft; heating said pile by means offlames from a burner above said pile, said flames directly impinging onsaid pile and transferringa quantity of heat of at least 150,000 kcal.per hour and per square meterto the surface ofsaid pile; admittingrinsing gas into the interior of said pile, said rinsing gas having atemperature of at least 900 to 1,000", C., whereby a carbonized skinisformed on the surface of the briquettes strong enough to preventbreaking of said briquettes; and discharging the coked briquettes at thesame rate as they arefedinto said shaft.

2. The process according to claim 1, which comprises admittingadditional gas for heating the top of the pile of fuel formed in theshaft in addition to the heating gas admitted to the interior of thepile.

References Cited in the file of this patent UNITED STATES PATENTS 5Rosenthol May 26, 1925 Hubmann Sept. 1, 1925 Hubmann Nov. 6, 1928Records Feb. 2, 1932 Wright July 12, 1932 Ackermann July 18, 1933

1. A PROCESS FOR COKING BRIQUETTES MADE OF SOLID FUEL IN A SHAFTFURNACE, WHICH COMPRISES FEEDING SOLID BRIQUETTED FUEL IN INTERVALS OF15 TO 60 MINUTES FROM THE TOP INTO SAID SHAFT SO AS TO FORM A PILE WITHA SLIDING UPPER SURFACE IN SAID SHAFT, HEATING SAID PILE BY MEANS OFFLAMES FROM A BURNER ABOVE SAID PILE, SAID FLAMES DIRECTLY IMPINGING ONSAID PILE AND TRANSFERRING A QUANTITY OF HEAT OF AT LEAST 150,000 KCAL.PER HOUR AND PER SQUARE METER TO THE SURFACE OF SAID PILE, ADMITTINGRINSING GAS INTO THE INTERIOR OF SAID PILE, SAID RINSING GAS HAVING ATEMPERATURE OF AT LEAST 900 TO 1,000*C., WHEREBY A CARBONIZED SKIN ISFORMED ON THE SURFACE OF THE BRIQUETTES STRONG ENOUGH TO PREVENTBREAKING OF SAID BRIQUETTES, AND DISCHARGING THE COKED BRIQUETTES AT THESAME RATE AS THEY ARE FED INTO SAID SHAFT.